HEAVY METALS
hen we as consumers hear the
words “heavy metals,” our minds
Wconjure
up the notorious skull and
crossbones. We prefer to avoid them at
all costs, and for good reason. Heavy
metals have been linked to serious
illnesses and conditions, such as
heart disease, cancer, neurological
conditions, and birth defects.
Over time, our bodies can accumulate these toxins from the foods
we eat, beverages we drink, air we
breathe, and cosmetics we apply to our
skin. How heavy metals enter those
substances in the first place, however,
is a different story. These toxins are
introduced into the environment from
an array of different sources.
For the sake of this article, we will
focus on one of these sources: plant
fertilizer. We’ll look at the presence and
transmission of heavy metals in plant
fertilizers, as well as how to optimize
plant nourishment toward a cleaner,
greener end product.
Defining Heavy Metals
Heavy metals are chemical elements
known for having very high densities.
In some forms, such as in golf clubs,
these heavy metals are helpful as they
are used to produce robust sporting
equipment. In other cases, such as with
accidental ingestion, these elements
can act as toxins.
Heavy metals may be present in trace
quantities as ions dissolved in soluble
solutions, such as in fertilizer. This form
allows the metal to enter the cell walls
of the host. There are nine heavy metals
that the Association of American Plant
Food Control Officials (AAPFCO), an
organization that limits and control the
presence of heavy metals in fertilizers
in order to make them safe for human
consumers, regulates: arsenic, cadmium,
cobalt, mercury, molybdenum, lead,
nickel, selenium, and zinc.
The AAPFCO is setting increasingly
uniform standards within the US fertilizer industry to align the practices of
manufacturers with the safety of their
consumers. In addition, the Department
of Agriculture (DOA) of each state has its
own set of standards and requirements a
fertilizer must pass in order to be registered for legal commercial sale.
Origin of Heavy Metals
Many heavy metals are by-products of
certain industrial processes, agricultural
runoff, consumer waste, and contaminated soils. In some cases, however,
these heavy metals exist naturally in
the environment. Rock phosphate, a
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Maximum Yield USA | December 2016
common ingredient used to produce
organic phosphate-based fertilizers, is
one example. Rock phosphate, in some
cases, contains high levels of arsenic.
On that same thread, the actual
heavy metal content in fertilizer ingredients varies depending on the region
and conditions in which the materials
were processed. For example, organic
fertilizers derived from fish emulsion
can contain higher levels of certain
metals, such as mercury, depending
on where the fish were raised and
what they absorbed or consumed
during their lifetime.
Other heavy metals, such as lead,
are found in soils where they have
had a chance to accumulate over time.
However, humans can avoid ingesting these heavy metals by thoroughly
washing soil off fruits or flowers before
consuming them.
“Many heavy
metals are byproducts of certain industrial processes,
agricultural runoff, consumer waste, and
contaminated soils.”